This invention relates to a lens holder driving device and, in particular, to a lens holder driving device capable of picking up a still image without blurry images by stabilizing the blurry images (movement) occurring upon shooting the still image using a miniature camera for a mobile terminal.
Hitherto, various lens holder driving devices has been proposed which are capable of taking photographs with a high degree by stabilizing blurry images on an image-forming surface although there are blurry images (movement) upon shooting the still image.
By way of illustration, two of the present co-inventors proposed an image stabilizer which is capable of miniaturizing and lowering a height by sharing a permanent magnet for an auto-focusing (AF) lens driving device as a permanent magnet for the image stabilizer (see, Japanese Unexamined Patent Application Publication No. 2011-65140 (JP-A-2011-065140) (which will be also called Patent Document 1)).
The image stabilizer disclosed in Patent Document 1 is called an image stabilizer of “a barrel shift method” because blurry images are stabilized by moving a lens barrel received in an AF lens driving device (a lens holder moving portion) in itself. In addition, the image stabilizers of “the barrel shift method” are classified into “a moving magnet method” in which the permanent magnet moves (is movable) and “a moving coil method” in which the coil moves (is movable).
Patent Document 1 discloses, as the image stabilizer of “the moving magnet method” in a second exemplary embodiment thereof, an image stabilizer which is provided with a permanent magnet comprising four first permanent magnet pieces and four second permanent magnet pieces which are disposed so as to apart from up and down in a direction of an optical axis and which is provided with a stabilizer coil disposed between the upper four first permanent magnet pieces and the lower four second permanent magnet pieces. That is, the second exemplary embodiment comprises the image stabilizer of “the moving magnet method” including the permanent magnet comprising eight permanent magnet pieces in total.
In the image stabilizer disclosed in Patent Document 1, a base is disposed so as to apart from at a bottom portion of the auto-focusing lens driving device and a plurality of suspension wires have one ends which are fixed to the base at outer regions thereof. The plurality of suspension wires has other ends which are firmly fixed to the auto-focusing lens driving device (the lens holder moving portion).
In the image stabilizer disclosed in Patent Document 1, the plurality of suspension wires swingably support the auto-focusing lens driving device (the lens holder moving portion). Therefore, there is a problem in which the auto-focusing lens driving device (the lens holder moving portion) resonates undesirably.
Japanese Unexamined Patent Application Publication No. 2011-85666 (JP-A-2011-085666) (which will be also called Patent Document 2) also discloses a lens driving device which shares an AF control magnet as an image stabilizer control magnet. The lens driving device disclosed in Patent Document 2 comprises a lens holder including a first coil (an AF coil) disposed at an outer periphery of a lens, a magnet holder configured to fix a magnet having a first surface facing the first coil, springs for supporting the lens holder so as to couple the lens holder with the magnet holder and also so that the lens holder is moved with respect to the magnet in a direction of an optical axis, and a base member configured so that a second coil (an image stabilizer coil) is fixed to face a second surface of the magnet that is perpendicular to the first surface thereof. A lens holding unit, which comprises the lens holder, the magnet, the magnet holder, and the springs, is held so as to be relatively movable in a direction perpendicular to the optical axis relative to the base member.
Patent Document 2 discloses the lens driving device as a six exemplary embodiment in which a position detection sensor is disposed at a clearance of the image stabilizer coil wound. A Hall element is used as the position detection sensor. In addition, the lens holding unit is held by four suspension wires which are disposed to a fixed portion at four corners thereof. That is, the four suspension wires have one ends fixed to the four corners of the fixed portion and other ends which are firmly fixed to the lens holding unit.
In also the lens driving device disclosed in Patent Document 2, the four suspension wires swingably support the lens holding unit. As a result, in the manner similar to the image stabilizer disclosed in Patent Document 1, there is a problem in which the lens holding unit resonates undesirably.
Accordingly, it is impossible to carry out operation with stability in the devices disclosed in Patent Documents 1 and 2.
On the other hand, Japanese Unexamined Patent Application Publication No. 2009-145771 (JP-A-2009-145771) (which will be also called Patent Document 3) discloses “an image stabilizing device” which is capable of reducing influence of unnecessary resonance. The image stabilizing device disclosed in Patent Document 3 comprises a movable member for holding stabilizing means for stabilizing blurred images, a fixed member supporting the movable member movably within a plane orthogonal to an optical axis of an image pickup optical system, driving means changing a relative position of the movable member with respect to the fixed member, and damping means disposed between the movable member and the fixed member. In Patent Document 3, by arranging the damping means to suitable positions, resonance of translational motion which is motion within the plane orthogonal to the optical axis and resonance by rotation around the optical axis are suppressed (attenuated).
The image stabilizing device disclosed in Patent Document 3 merely suppresses (attenuates) the resonance by movement (the translational motion and the rotation around the optical axis) on the plane orthogonal to the optical axis.